1. Field of the Invention
The invention relates to the field of television and, more particularly, an object of the invention is a device for assistance in the optical focusing of a television camera and a camera provided with such a device.
The optical focusing of a television camera is done by adjusting the focus of the objective lens mounted on the camera.
This adjustment can be done by the cameraman who focuses his camera by controlling the fineness of his image on a small television monitor or viewfinder, fixed on the camera, and who also centers the image as instructed by the director.
The task of focusing the image is therefore entrusted to the cameraman, and the only check is the one done through the image in the viewfinder.
The precision of the focusing therefore depends on the fineness and size of the viewfinder and practically rules out the use of a color viewfinder with a resolution smaller than that of black and white viewfinders.
In high-definition television, the definition of the image is doubled, vertically and horizontally, in relation to a standard image. The precision required of the cameraman for the focusing of the image should therefore be four times greater.
The limited size of the viewfinders that can be set up on a camera means that it is not always possible to obtain this increased precision. It is therefore frequently the case that high-definition images are not focused to the optimum degree. This is detrimental to promoting the use of this standard.
2. Description of the Related Prior Art
In certain high-definition cameras, manufacturers have introduced a focusing remote control unit on the desk of the vision controller who has a control monitor with higher resolution than that of the viewfinder. However, the vision controller does not have the cameraman's artistic sense, and does not necessarily know how or where to aim the camera.
Moreover, this system cannot be used in the very frequent case were several cameras are used. One vision engineer cannot control the focusing on several cameras at the same time.